Process for recovering a dialkylarylketone

ABSTRACT

A process for recovering a dialkylarylketone from an oily mixture containing largely a 1,1-diaryl-2-nitroethylene as contaminant which comprises heating the oily mixture to a temperature of at least about 140 DEG  C. and then recovering solid dialkylarylketone from a solvent solution of the 1,1-diaryl-2-nitroethylene.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention defined herein relates to a process for recovering adi(alkylaryl)ketone, normally solid at room temperature (26° C), from onoily liquid mixture containing the same

2. Description of the Prior Art

In our U.S. patent application Ser. No. 581,288, filed May 27, 1975 nowU.S. Pat. No. 4,018,828, entitled Process for Recovering aDialkylarylketone, we found we were able to recover a dialkylarylketone,particularly tetramethylbenzophenone, from an oily mixture containinglargely the corresponding 1,1-diaryl-2-nitroethylene as a contaminant byadding a base, such as sodium hydroxide, to the mixture untilsolidification occurred and then effecting the desired recovery ofbenzophenone from a suitable solvent.

SUMMARY OF THE INVENTION

The process defined and claimed herein relates to the recovery of adialkylarylketone, specifically, 3,4,3',4'-tetramethylbenzophenone (TMB)or 4,4'-dimethylbenzophenone (DMB), from on oily mixture contaminatedlargely with a 1,1-diaryl-2-nitroethylene, specifically,1,1-di(3,4-dimethylphenyl)-2-nitroethylene when TMB is thedialkylarylketone, or 1,1-di(4-methylphenyl)-2-nitroethylene when DMB isthe dialkylarylketone, which comprises heating the mixture to atemperature of at least about 140° C. and then recovering thedialkylarylketone from a solvent solution of the1,1-diaryl-2-nitroethylene.

BRIEF DESCRIPTION OF THE PROCESS

The oily mixture being treated herein will contain the followingcomponents in the following amounts:

    ______________________________________                                                             Parts by Weight                                                               Broad  Narrow                                                                 Range  Range                                             3,4,3',4'-tetramethylbenzophenone (TMB)                                       or 4,4'-dimethylbenzophenone (DMB)                                                                   25 to 95 55 to 90                                      1 1-di(3,4-dimethylphenyl)-2-nitro-                                           ethylene (DMPE)                                                               or 1,1-di(4-methylphenyl)-2-nitro-                                            ethylene (MPE)          5 to 40 10 to 30                                      1,1-di(3,4-dimethylphenyl)ethanol (DMPET)                                     or 1,1-di(4-methylphenyl)ethanol (MPET)                                                              0 to 5   0 to 2                                        Compounds corresponding to the above                                          wherein one or more methyl substituents                                       are converted to carboxyl                                                                             0 to 15 0 to 5                                        1,1-bis(3,4-dimethylphenyl)ethane (DXE)                                       or 1,1-bis(ρ-tolyl)ethane (DTE)                                                                   0 to 50  0 to 25                                      ______________________________________                                    

In a preferred embodiment, the oily mixture treated herein is obtainedas a result of the nitric acid oxidation of DXE or DTE at a temperaturebelow about 140° C., but above about 70° C., using critical amounts ofnitric acid and water as defined and claimed, for example, in ourapplication Ser. No. 581,287, filed May 27, 1975 now U.S. Pat. No.4,022,838, entitled Process for Preparing Diarylketones.

In accordance with our discovery, we heat the oily mixture defined aboveto a temperature of at least about 140° C., preferably at least about160° C., but no higher than about 300° C., preferably no higher thanabout 225° C., for at least about 1 minute, preferably at least about 15minutes, but generally no longer than about 2 hours, preferably nolonger than about 60 minutes. Pressures are not critical and thereforeany suitable pressure can be used. Thus the pressure can be from about14.7 pounds per square inch gauge, or atmospheric, (about 1 kilogram persquare centimeter) to about 1000 pounds per square inch gauge (about 68kilograms per square centimeter), preferably about 14.7 pounds persquare inch gauge to about 300 pounds per square inch gauge (about 20kilograms per square centimeter).

As a result of such heating, the oily mixture will unexpectedly solidifyto form particulate solids, generally yellow to pale green in color. TheTMB or DMB present is recovered from said solids by recrystallizationfrom a solvent. Any solvent in which TMB or DMB is substantiallyinsoluble at room temperature but the remaining compounds associatedtherewith are substantially soluble can be used. Examples of solventssuitable herein include alcohols, such as methanol, ethanol andisopropanol; esters, such as methyl acetate, ethyl acetate and methylformate; ketones, such as acetone, methylethylketone and cyclohexanone;organic acids, such as acetic acid and propionic acid; ethers, such astetrahydrofuran an dioxane; hydrocarbons, such as benzene, toluene,n-hexane and n-heptane; chlorinated hydrocarbons, such as carbontetrachloride, methylene chloride, chloroform and chlorobenzenes;"super-solvents", such as dimethylsulfoxides, dimethylformamide andhexamethylphosphoramide; carbon disulfide; etc. The amount of solventused can vary over a wide limit, but in general the weight ratio ofsolid to solvent will be in the range of about 1:100 to about 1:1,preferably in the practical range of about 5:100 to about 1:4.

The recrystallization of TMB or DMB is easily effected. The solids,defined above, are stirred with the solvents, defined above, at atemperature of from about 26° C. to about 200° C., preferably from about26° C. to about 100° C., and a pressure in the ranges defined in theheating step above for a time sufficient to obtain a homogeneoussolution, for example, from about 5 minutes to about 1 hour, preferablyabout 10 to about 30 minutes. At the end of this period, the homogeneousmixture is allowed to cool to a temperature of about 0° to about 100°C., preferably about 25° to about 45° C., over a period of about 15minutes to about 2 hours, preferably about 30 to about 60 minutes, as aresult of which the TMB or DMB will recrystallize out of solution.Simple mechanical separation, for example, filtration, will result inthe recovery of TMB or DMB. The filtrate will contain the compoundsassociated with the TMB or DMB. If the former may still contain someimpurities after the above separation, further recrystallization of theTMB or DMB from the solvents, as defined above, will result in a furtherpurification thereof.

An alternative separation procedure to the one defined above involvesadding the solvent to the oily mixture prior to the initial heating, butotherwise identical thereto.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE I

Into a 1-liter, three-necked, round-bottomed flask equipped with acondenser, thermometer and stirrer there was added 140 grams of DXE, 330grams of water and 75 grams of 70 percent aqueous nitric acid. Themixture was heated under reflux (100° C.,) and atmospheric pressure(14.7 pounds per square inch gauge, or 1 kilogram per square centimeter)for 4 hours. After the reaction mixture was cooled to about 0° C., theresulting aqueous layer was separated from the organic layer bydecantation. The organic layer of 178 grams lost about 3.1 grams ofwater upon evaporation to dryness in a rotary evaporator. Analysis ofthe organic oily liquid (175 grams) by gas chromatography showed thefollowing composition: 15.2 weight percent DXE, 73.9 weight percent TMB,9.6 weight percent nitroolefin, and 1.3 weight percent unidentifiedproducts. Attempts to isolate TMB from the oily mixture by the followingseries of experiments were unsuccessful.

From about 2.0 to about 2.5 grams of the oily product obtained abovewere added to each of the following solvents at room temperature andatmospheric pressure (14.7 pounds per square inch gauge) while stirring:methanol, acetone, n-hexane, benzene, ethyl acetate, carbontetrachloride, acetic acid, p-dioxane, tetrahydrofuran, chloroform andisopropanol. In each instance the product dissolved readily. Eachsolution was seeded by adding approximately 0.1 gram of pure TMB in anattempt to prompt crystallization of the TMB in the product. Nocrystallization occurred, even at the end of one day. An attempt wassimilarly made to seed about 2.5 grams of the oily product, in theabsence of a solvent, with pure TMB, but this effort was similarlyunsuccessful.

Each of the above solutions was heated at the reflux temperature of therespective solvents for about 15 to 20 minutes and then permitted tocome to room temperature and stand for one to two hours. No solids wereformed.

Each of the above solutions was then cooled in a dry ice-acetone mixtureto about -70° C. and maintained at said temperature for about 10 to 20minutes until solids formed. The cooled product was permitted to come toroom temperature, at which point everything was in solution.

Finally, each of the above solutions was concentrated by evaporation ona steam bath until about 2/3 of the solvent was evaporated therefrom.The solution was permitted to come to room temperature, but no solidformation occurred.

EXAMPLE II

A 700-ml, 314 stainless steel autoclave (Autoclave Engineers Inc., Erie,Pa.) was charged with 140 grams of DXE and 70 grams of water and thenheated to a temperature of about 100° C., developing a pressure of 17pounds per square inch gauge (1.2 kilograms per square centimeter). Atthis temperature a mixture of 100 grams of 70 percent aqueous nitricacid and 150 grams of water was added to the reactor over a period of105 minutes. Reaction was continued for an additional hour at 100° C. toa final pressure of about 186 pounds per square inch gauge (13 kilogramsper square centimeter). The reactor was cooled to room temperature,depressured at atmospheric pressure and the aqueous solution withdrawntherefrom by suction. The organic oily layer was transferred to a flask,using small amounts of acetone to recover residual material stuck to thewalls of the autoclave, and then subjected to evaporation in a rotaryevaporator to remove acetone therefrom. A total of 172.4 grams of anoily, viscous fluid was recovered having the following composition: 61.8weight percent TMB, 14.7 weight percent nitroolefin, 6.6 weight percentunidentified products and 16.9 weight per cent DXE. DXE conversionamounted to 80.0 percent. The oily product was found to be completelysoluble in common organic solvents, including benzene, acetone andmethanol, at room temperature and atmospheric pressure. When 95 grams ofthe oily product was subjected to distillation under a vacuum of 3millimeters of mercury in order to effect a separation of itscomponents, unexpectedly before any distillation took place, at a pottemperature of about 150° C., the entire material in the distillationflask solidified to a yellow solid. The remainder of the oily productwas transferred back to the reactor and simply heated to a temperatureof 175° C. at autogeneous pressure for 15 minutes and then cooled toroom temperature (25° C.). Again, the product was a yellow solid. 70grams of these solids were stirred with 200 cubic centimeters ofn-hexane at room temperature and room pressure for 5 minutes and theresultant mixture was filtered to recover free-flowing solids of thefollowing composition: 73.1 weight percent TMB, 19.6 weight percentnitroolefin, 2 weight percent DXE and 4.4 weight percent unidentifiedproducts. 20 grams of the recovered product were dissolved by stirringin 100 cubic centimeters of methanol at 35° C. and atmospheric pressure.On standing at room temperature for 30 minutes solid product started toprecipitate out of solution. Upon filtration, 17.1 grams of a solidproduct containing 98 weight percent TMB was recovered.

EXAMPLE III

A mixture containing 30 grams of DXE, 330 grams of water and 75 grams of70 aqueous nitric acid was heated at atmospheric pressure and atemperature of 100° C. for 3.5 hours. At the end of the reaction, themixture was cooled to room temperature and the aqueous phase wasseparated from the oily liquid organic phase by decantation. Analysis bygas chromatography showed the product to have the following composition:10.6 weight percent DXE, 62.0 weight percent TMB, 25.8 weight percentnitroolefin and 1.6 weight percent unidentified products. The productwas diluted with methanol to a final volume of about 240 milliliters andheated to 165° C. and atmospheric pressure for about 30 minutes. Theresulting product was cooled to room temperature and filtered to recover12.7 grams of light tan, free-flowing, solid containing 95.4 weightpercent TMB. Further recrystallization of this product from 20 cubiccentimeters of methanol which had been heated to a temperature of 40° C.for 10 minutes and cooled to room temperature and maintained at thelatter temperature for about 30 minutes, increased the purity of ketoneto 98 percent.

EXAMPLE IV

The nitric acid oxidation reaction described in Example II was repeatedto obtain an oily mixture analyzing as follows: 62.4 weight percent TMB,16.6 weight percent nitroolefin, 14.8 weight percent DXE and 6.2 weightpercent unidentified products. This mixture was divided into two equalportions, the first was diluted with 200 cubic centimeters of ethylacetate and the second with 200 cubic centimeters of tetrahydrofuran.Each of the solutions was heated, while stirring, to about 165° C. andautogeneous pressure for about 15 to 20 minutes and then cooled to roomtemperature and maintained at the latter temperature for 60 minutes.Each of the resulting mixtures was filtered to recover a free-flowingsolid. The solids obtained from treatment with ethyl acetate were foundto contain 95.1 weight percent TMB, those obtained as a result oftreatment with tetrahydrofuran were found to contain 96.2 weight percentTMB.

Obviously, many modifications and variations of the invention, ashereinabove set forth, can be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:
 1. A process for recovering a dialkylarylketone selected fromthe group consisting of 3,4,3',4'-tetramethylbenzophenone and4,4'-dimethylbenzophenone from an oily mixture contaminated largely withthe corresponding 1,1-diaryl-2-nitroethylene, said oily mixture havingbeen obtained as a result of the nitric acid oxidation of a diarylalkaneselected from the group consisting of 1,1-bis(p-tolyl)ethane and1,1-bis(3,4-dimethylphenyl) ethane at a temperature below about 140° C.which comprises heating said mixture to a temperature of at least about140° until solidification occurs and then recovering thedialkylarylketone as a solid from a solvent solution of the1,1-diaryl-2-nitroethylene, said solvent being selected from the groupconsisting of alcohols, esters, ethers and hydrocarbons.
 2. The processof claim 1 wherein said dialkylarylketone is3,4,3',4'-tetramethylbenzophenone.
 3. The process of claim 1 whereinsaid dialkylarylketone is 4,4'-dimethylbenzophenone.
 4. The process ofclaim 1 wherein said heating is effected at a temperature of about 140°to about 300° C.
 5. The process of claim 1 wherein said heating iseffected at a temperature of about 160° to about 225° C.
 6. The processof claim 1 wherein the product obtained upon said heating involvesdissolving in said solvent, in which said 1,1-diaryl-2-nitroethylene issoluble, at a temperature of about 24° to about 200° C., cooling to atemperature of about 0° to about 100° C. until solid dialkylarylketoneprecipitates out of solution and then recovering said dialkylarylketonefrom said solution.
 7. The process of claim 1 wherein the productobtained upon said heating involves dissolving in said solvent, in whichsaid 1,1-diaryl-2-nitroethylene is soluble, at a temperature of about24° to about 100° C., cooling to a temperature of about 25° to about 45°C. until solid dialkylarylketone precipitates out of solution and thenrecovering said dialkylarylketone from said solution.
 8. The process ofclaim 6 wherein said solvent is n-hexane.
 9. The process of claim 6wherein said solvent is methanol.
 10. The process of claim 6 whereinsaid solvent is ethyl acetate.
 11. The process of claim 6 wherein saidsolvent is tetrahydrofuran.
 12. The process of claim 1 wherein saidheating is carried out in the presence of said solvent, in which said1,1-diaryl-2-nitroethylene is soluble, the heated mixture is cooled to atemperature of about 0° to about 100° C. until solid dialkylarylketoneprecipitates out of solution and then recovering dialkylarylketone fromsaid solution.
 13. The process of claim 1 wherein said heating iscarried out in the presence of said solvent, in which said1,1-diaryl-2-nitroethylene is soluble, the heated mixture is cooled to atemperature of about 25° to about 45° C. until solid dialkylarylketoneprecipitates out of solution and then recovering dialkylarylketone fromsaid solution.
 14. The process of claim 12 wherein said solvent isn-hexane.
 15. The process of claim 12 wherein said solvent is methanol.16. The process of claim 12 wherein said solvent is ethyl acetate. 17.The process of claim 12 wherein said solvent is tetrahydrofuran.
 18. Theprocess of claim 6 wherein the weight ratio of the heated product to thesolvent is in the range of about 1:100 to about 1:1.
 19. The process ofclaim 6 wherein the weight ratio of the heated product to the solvent isin the range of about 5:100 to about 1:4.
 20. The process of claim 12wherein the weight ratio of the heated product to the solvent is in therange of about 1:100 to about 1:1.
 21. The process of claim 12 whereinthe weight ratio of the heated product to the solvent is in the range ofabout 5:100 to about 1:4.
 22. The process of claim 1 wherein said oilymixture is obtained as a result of the nitric acid oxidation of1,1-bis(3,4-dimethylphenyl) ethane.
 23. The process of claim 1 whereinsaid oily mixture is obtained as a result of the nitric acid oxidationof 1,1-bis(ρ-tolyl) ethane.
 24. The process of claim 6 wherein saidrecovery is effected by filtration.
 25. The process of claim 12 whereinsaid recovery is effected by filtration.